(1) Field of the Art
This invention relates to a die forging press.
(2) Description of the Prior Art
As is well known in the art, dies need to be preheated in hot forging, especially in precision die forging which employs dies of relatively large volumes as compared with the size of the products. Normally, a die set is assembled outside a press machine and heated from its outer periphery in that state before setting the same on the press machine, controlling its temperature such that it will retain an appropriate temperature on the press machine.
In the die forging operation, it is required to maintain an appropriate temperature at those die portions which contact the forging material and particularly at those portions proximate to the opposing meeting faces of the upper and lower dies. Therefore, the above-mentioned conventional method of heating the upper and lower dies in an assembled state necessarily involves the heating of those die portions which do not need to be heated to the appropriate die temperature, resulting in a low heating efficiency and a large energy loss. Moreover, there has been a strong demand for improvement of the working conditions so as to minimize the hot and heavy labor which has thus far been required for transferring and mounting the heated dies on the press machine.
On the other hand, in order to replace the dies in a prompt and accurate manner, the best method is to assemble the upper and lower dies outside the press machine and to bring them into the machine in that state. However, this provokes an antinomy against the above-mentioned problem of economical heating which necessitates opening of the dies for heating the die portions which need heat control.